Method for producing fluoride phosphor

ABSTRACT

Provided is a method for producing a fluoride phosphor. The method includes: providing a first solution containing an element M 1  containing at least one selected from the group consisting of group 13 elements, manganese, and fluorine, a second solution containing an element M 2  containing at least one selected from the group consisting of group 4 elements and group 14 elements, and a third solution containing at least one selected from the group consisting of alkali metal elements; and adding the second solution and the third solution to the first solution at substantially the same time.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2021-110955, filed on Jul. 2, 2021, the disclosure of which is herebyincorporated by reference in its entirety.

BACKGROUND Field of the Invention

The present disclosure relates to a method for producing a fluoridephosphor.

DESCRIPTION OF THE RELATED ART

Light emitting devices obtained by combining light emitting elements andphosphors are used in a wide range of fields such as lighting,on-vehicle lighting, displays, and liquid crystal backlights. Forexample, a phosphor used in a light emitting device for a liquid crystalbacklight is required to have high color purity, i.e., a narrowhalf-value width of a luminescence peak. Japanese Laid-Open PatentPublication No. 2010-254933 discloses a fluoride phosphor activated withtetravalent manganese as a red light-emitting phosphor having a narrowhalf-value width of a luminescence peak.

SUMMARY

According to a first exemplary embodiment is provided a method forproducing a fluoride phosphor, and the method includes: providing afirst solution containing an element M¹ containing at least one selectedfrom the group consisting of group 13 elements, manganese, and fluorine,a second solution containing an element M² containing at least oneselected from the group consisting of group 4 elements and group 14elements, and a third solution containing at least one selected from thegroup consisting of alkali metal elements; and adding the secondsolution and the third solution to the first solution at substantiallythe same time to obtain a first fluoride phosphor. According to anexemplary embodiment of the present disclosure, a method formanufacturing a fluoride phosphor capable of improving a luminous fluxin a light emitting device can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing an exemplary lightemitting device including a fluoride phosphor.

DETAILED DESCRIPTION

The term “step” as used herein comprises not only an independent stepbut also a step not clearly distinguishable from another step as long asthe intended purpose of the step is achieved. If multiple substancescorrespond to a component in a composition, the content of the componentin the composition means the total amount of the multiple substancespresent in the composition unless otherwise specified. An upper limitand a lower limit of a numerical range described herein can arbitrarilybe selected and combined. In this description, a relationship between acolor name and a chromaticity coordinate, a relationship between awavelength range of light and a color name of monochromatic light, etc.comply with HS 28110. A half-value width of a phosphor and a lightemitting element means a wavelength width (full width at half maximum;FWHM) of the emission spectrum in which the emission intensity is 50% ofthe maximum emission intensity in the emission spectrum of the phosphorand the light emitting element. The median diameter of the phosphor is avolume-based median diameter and refers to a particle size correspondingto a volume accumulation of 50% from the small diameter side in thevolume-based particle size distribution. The particle size distributionof the phosphor is measured by a laser diffraction method using a laserdiffraction type particle size distribution measuring device. Theaverage particle size of the phosphor is F.S.S.S.No. (Fisher Sub SieveSizer's No.) obtained by the air permeation method and is measured byusing, for example, Fisher Sub-Sieve Sizer Model 95 manufactured byFisher Scientific. Embodiments of the present invention will now bedescribed in detail. However, the embodiments described below exemplifya method for manufacturing a fluoride phosphor for embodying thetechnical idea of the present invention, and the present invention isnot limited to the method for manufacturing a fluoride phosphordescribed below.

Method for Producing Fluoride Phosphor

The method for producing a fluoride phosphor according to an exemplaryembodiment of the present disclosure may include a providing step ofproviding a first solution containing an element M¹ containing at leastone selected from the group consisting of group 13 elements, manganese,and fluorine, a second solution containing an element M² containing atleast one selected from the group consisting of group 4 elements andgroup 14 elements, and a third solution containing at least one selectedfrom the group consisting of alkali metal elements, and a synthesis stepof synthesizing a fluoride phosphor by adding the second solution andthe third solution to the first solution at substantially the same timeto obtain a first fluoride phosphor.

A light emitting device including a fluorescent member containing afluoride phosphor obtained by mixing three solutions having differentcomponents to synthesize a fluoride phosphor may achieve a high luminousflux and is excellent in durability. This may be probably because, forexample, the components constituting the fluoride phosphor divided intothree solutions are combined at the time of synthesis of the fluoridephosphor, so that particularly the distribution of the group 13 elementis more uniformly controlled and, therefore, crystals of a fluoridephosphor having a more uniform desired composition are formed.

Providing Step

In the providing step, the first solution containing the element M¹,manganese (Mn), and fluorine (F), the second solution containing theelement M², and the third solution containing the alkali metal elementare provided.

The first solution contains the elements M¹, manganese and fluorine. Theelement M¹ includes at least one selected from the group consisting ofthe group 13 elements and may further include an element other than thegroup 13 elements as needed. Examples of the group 13 element includeboron (B), aluminum (Al), gallium (Ga), and indium (In). The element M¹contained in the first solution may preferably contain at least Al. Theratio of the number of moles of Al to the total number of moles of theelement M¹ contained in the first solution may be, for example, 90 mol %or more, preferably 95 mol % or more, or 98 mol % or more. The elementM¹ may be contained in the first solution as an ion or a complex ion ormay be contained as a compound containing the element M¹.

Examples of an element M¹ source constituting the first solution includecompounds containing the element M¹ such as a salt of the element M¹, ahydroxide of the element M¹, and an oxide of the element M¹. Examples ofthe salt of the element M¹ include halides containing halogens such asfluorine and chlorine, sulfates, and nitrates. One type of the elementM¹ source constituting the first solution may be used alone, or two ormore types thereof may be used in combination. Specifically, when the M¹source contains aluminum (Al), examples of the aluminum compound servingas the M¹ source include hydroxides such as Al(OH)₃ andhexafluoroaluminates such as K₃AlF₆.

The element M¹ source concentration in the first solution may be, forexample, 0.01 mass % or more and 15.0 mass % or less, preferably 0.05mass % or more, or 0.1 mass % or more and may be preferably 10.0 mass %or less, or 5.0 mass % or less.

The manganese contained in the first solution may be in the form ofmanganese ions or first complex ions containing manganese ions. Themanganese ion may contain, for example, tetravalent manganese ions. Amanganese source may be a compound containing manganese, and specificexamples thereof include K₂MnF₆, KMnO₄, and K₂MnCl₆. Among them,hexafluoromanganese such as K₂MnF₆ may stably be present in hydrofluoricacid as MnF₆ complex ions while maintaining the oxidation number(tetravalent) capable of activating the fluoride phosphor and istherefore preferable. Among the manganese sources, those containing analkali metal such as potassium may also serve as a portion of an alkalimetal source contained in the third solution. One type of the manganesesource constituting the first solution may be used alone, or two or moretypes thereof may be used in combination.

The lower limit of the manganese concentration in the first solution maybe, for example, 0.01 mass % or more, preferably 0.03 mass % or more,0.05 mass % or more, or 0.1 mass % or more. The upper limit of themanganese concentration in the first solution may be, for example, 50mass % or less, preferably 40 mass % or less, 30 mass % or less, or 10mass % or less.

The fluorine contained in the first solution may be in the form offluoride ions, hydrogen fluoride, or complex ions containing fluorideions. The lower limit of the concentration of fluorine in the firstsolution, for example, as a hydrogen fluoride concentration, may be, forexample, 20 mass % or more, preferably 25 mass % or more, or 30 mass %or more. The upper limit of the hydrogen fluoride concentration in thefirst solution may be, for example, 80 mass % or less, preferably 75mass % or less, or 70 mass % or less. When the hydrogen fluorideconcentration is 30 mass % or more, the stability of the manganesesource (e.g., K₂MnF₆) constituting the first solution to hydrolysis isimproved, and the fluctuation of the tetravalent manganese concentrationin the first solution is suppressed. As a result, an amount of activatedmanganese contained in the obtained fluoride phosphor may easily becontrolled, and the variation or fluctuation in the luminous efficiencyin the fluoride phosphor tends to be suppressed. When the hydrogenfluoride concentration is 70 mass % or less, a decrease in the boilingpoint of the first solution is suppressed, and the generation ofhydrogen fluoride gas is suppressed. As a result, the hydrogen fluorideconcentration in the first solution may easily be controlled, and thevariation or fluctuation in the particle diameter of the obtainedfluoride phosphor may effectively be suppressed.

The first solution may be prepared, for example, by mixing anddissolving the element M¹ source, the manganese source, and the fluorinesource in a liquid medium. The liquid medium constituting the firstsolution may contain at least water and may be a hydrofluoric acidaqueous solution also serving as the fluorine source in the firstsolution. The first solution may preferably be prepared by dissolvingthe element M¹ source and the manganese source in a hydrofluoric acidaqueous solution.

The second solution contains the element M². The element M² includes atleast one selected from the group consisting of the group 4 elements andthe group 14 elements and may further contain an element other than thegroup 4 elements and the group 14 elements, if necessary. Examples ofthe group 4 elements include titanium (Ti), zirconium (Zr), and hafnium(Hf) Examples of the group 14 elements include carbon (C), silicon (Si),germanium (Ge), tin (Sn), and lead (Pb). The element M² contained in thesecond solution may preferably contain at least one selected from thegroup consisting of at least Ti, Zr, Hf, Si, Ge, and Sn, may contain Sior Si and Ge, and may contain at least Si. The ratio of the number ofmoles of Si to the total number of moles of the element M² contained inthe second solution may be, for example, 90% or more, preferably 93% ormore, or 95% or more. The element M² may be contained in the secondsolution as ions, complex ions, or a compound containing the element M².

The lower limit of the element M² source concentration in the secondsolution may be, for example, 1 mass % or more, preferably 2 mass % ormore, or 3 mass % or more. The upper limit of the element M² sourceconcentration in the second solution may be, for example, 50 mass % orless, preferably 40 mass % or less, 30 mass % or less, or 10 mass % orless.

The second solution may contain at least second complex ions containingthe element M² and fluorine ions as the element M² source. For example,when the second complex ions contain Si, a second complex ion source ispreferably a compound containing silicon and fluorine and havingexcellent solubility in a solution. Specific examples of the secondcomplex ion source include H₂SiF₆, Na₂SiF₆, (NH₄)₂SiF₆, Rb₂SiF₆, andCs₂SiF₆. Among them, H₂SiF₆ has high solubility in water and does notcontain an alkali metal element as an impurity and is thereforepreferable. One type of the second complex ion source constituting thesecond solution may be used alone or two or more types thereof may beused in combination.

When the second solution contains H₂SiF₆ (hexafluorosilicic acid) as theelement M² source, the content of hexafluorosilicic acid relative to thetotal content of the element M² source may be, for example, 80% or more,preferably 90% or more, or 95% or more, or substantially onlyhexafluorosilicic acid may be contained. In an exemplary embodiment, thesecond solution may consist essentially of hexafluorosilicic acid andwater. As used herein, “substantially” means that impurities are allowedto be inevitably mixed.

The second solution may be prepared, for example, by dissolving theelement M² source in a liquid medium. The liquid medium may contain atleast water, for example. In an embodiment, the second solution may beprepared by dissolving the element M² source (e.g., hexafluorosilicicacid) in water.

The third solution contains an alkali metal. Examples of the alkalimetal include lithium (Li), sodium (Na), potassium (K), rubidium (Rb),and cesium (Cs), and may contain at least one selected from the groupconsisting of these. The alkali metal may contain at least K. The ratioof the number of moles of K to the total number of moles of alkali metalcontained in the third solution may be, for example, 0.8 or more,preferably 0.9 or more, or 0.95 or more. The alkali metal may becontained as ions in the third solution.

A portion of the alkali metal contained in the third solution may bereplaced with ammonium ions (NH₄ ⁺). When a portion of the alkali metalis replaced with ammonium ions, the ratio of the number of moles ofammonium ions to the total number of moles of alkali metal contained inthe third solution may be, for example, 0.10 or less, preferably 0.05 orless, or 0.03 or less. The lower limit of the ratio of the number ofmoles of ammonium ions may be, for example, more than 0, preferably0.005 or more.

The lower limit of the alkali metal source concentration in the thirdsolution may be, for example, 3 mass % or more, preferably 5 mass % ormore, or 10 mass % or more. The upper limit of the alkali metal sourceconcentration in the third solution may be, for example, 70 mass % orless, preferably 60 mass % or less, 50 mass % or less, or 40 mass % orless.

The third solution may be prepared, for example, by dissolving an alkalimetal element source in a liquid medium. Examples of the alkali metalsource include halides, hydroxides, acetates, and carbonates of alkalimetal. Specific examples of the alkali metal source includewater-soluble potassium salts such as KF, KHF₂, KOH, KCl, KBr, KI,CH₃COOK, and K₂CO₃. Among these, KHF₂ may be dissolved without loweringthe concentration of hydrogen fluoride in the third solution, is highlysafe because of little heat of dissolution, and is therefore preferable.Examples of the alkali metal source other than the potassium sourceinclude NaHF₂, Rb₂CO₃, and Cs₂CO₃. One type of the alkali metal sourceconstituting the third solution may be used alone or two or more typesthereof may be used in combination.

The liquid medium constituting the third solution may contain at leastwater, for example. The third solution may further contain hydrogenfluoride, and the liquid medium may be a hydrofluoric acid aqueoussolution. The lower limit of the hydrogen fluoride concentration in thethird solution may be, for example, S mass % or more, preferably 10 mass% or more, or 15 mass % or more. The upper limit of the hydrogenfluoride concentration in the third solution may be, for example, 80mass % or less, preferably 70 mass % or less, 60 mass % or less, or 50mass % or less.

The third solution may be prepared, for example, by dissolving an alkalimetal source in a liquid medium. In an embodiment, the third solutionmay be prepared by dissolving an alkali metal source (e.g., KHF₂) in anaqueous hydrofluoric acid solution.

Synthesis Step

In the synthesis step, the second solution and the third solution areadded to the provided first solution at substantially the same time tosynthesize a fluoride phosphor. By mixing the first solution, the secondsolution, and the third solution, manganese, the alkali metal ions, theions containing the element M¹, and the ions containing the element M²react at a predetermined ratio to precipitate crystals of the desiredfluoride phosphor including the first fluoride phosphor.

In the synthesis step, the second solution and the third solution areadded to the first solution. Adding at substantially the same time meansthat the addition of the second solution and the addition of the thirdsolution are performed in an overlapping manner. Therefore, the start ofaddition of the second solution and the start of addition of the thirdsolution may not necessarily coincide with each other, and the end ofaddition of the second solution and the end of addition of the thirdsolution may not necessarily coincide with each other. The addition ofthe second solution to the first solution and the addition of the thirdsolution to the first solution may be performed independently or eachother. Therefore, a flow path for adding the second solution may beseparated from a flow path for adding the third solution.

In the synthesis step, the second solution and the third solution may beadded while stirring the first solution. The stirring method mayappropriately be selected from methods usually used depending on aproducing scale, a reaction tank, etc. Regarding the temperature in thesynthesis step, for example, the temperature of the first solution maybe controlled to 5° C. or higher and 50° C. or lower, or 15° C. orhigher and 30° C. or lower.

The addition of the second solution and the third solution in thesynthesis step may be performed dropwise to the first solution or may becontinuous addition. Regarding the addition rate, for example, theaddition amount of each of the prepared second and third solutions perminute may be 1 vol. % or more and 20 vol. % or less of each of theinitial liquid amounts and may be preferably 3 vol. % or more and 15vol. % or less of the initial liquid amount. The time required foradding the second solution and the time required for adding the thirdsolution in the synthesis step may appropriately be selected dependingon the respective prepared liquid amounts etc. The time required foradding the second solution and the third solution may be, for example, 1minute or more and 20 minutes or less, preferably 2 minutes or more and15 minutes or less. The time required for adding the second solution andthe time required for adding the third solution may be the same ordifferent and may be preferably the same.

In an embodiment of the method for producing a fluoride phosphor, thesecond solution and the third solution are added independently andsubstantially simultaneously to the first solution to mix the threesolutions. In another embodiment of the method for producing a fluoridephosphor, the first solution and the second solution may be added to thethird solution independently and substantially simultaneously to mix thethree solutions, the first solution and the third solution may be addedto the second solution independently and substantially simultaneously tomix the three solutions, or the first solution, the second solution, andthe third solution may each be added to the same container independentlyand substantially simultaneously to mix the three solutions.

When mixing the first solution, the third solution, and the thirdsolution, considering a difference between the charged composition ofthe first solution, the second solution, and the third solution, and thechemical composition of the obtained fluoride phosphor, it is preferableto appropriately adjust the mixing ratio of the first solution, thesecond solution, and the third solution so that the desired chemicalcomposition of the fluoride phosphor is achieved as a product.

The fluoride phosphor precipitated in the synthesis step may berecovered by solid-liquid separation by filtration etc. The fluoridephosphor may be washed with a solvent such as ethanol, isopropylalcohol, water, and acetone. A drying treatment may further beperformed, and the drying is usually performed at 50° C. or higher,preferably 55° C. or higher, more preferably 60° C. or higher, andusually 150° C. or lower, preferably 120° C. or lower, more preferably110° C. or lower. The drying time may be any time as long as at least apart of the water adhering to the fluoride phosphor may be evaporatedand is about 10 hours for example.

The method for producing a fluoride phosphor may further include a heattreatment step of heat-treating the obtained first fluoride phosphor incontact with a fluorine-containing substance at a heat treatmenttemperature of 400° C. or higher to obtain a heat-treated secondfluoride phosphor.

By heat-treating the first fluoride phosphor in contact with thefluorine-containing compound, fluorine atoms are supplied to a regionwhere fluorine atoms are deficient in the crystal structure of thefluoride phosphor, so that defects in the crystal structure areconsidered to be further reduced. This probably further improves theluminance. Additionally, this probably further improves the durabilityof the fluoride phosphor.

The fluorine-containing substance used in the heat treatment step may bein a solid state, a liquid state, or a gaseous state at roomtemperature. Examples of the fluorine-containing substance in the solidstate or the liquid state include NH₄F. Examples of thefluorine-containing substance in the gaseous state include F₂, CHF₃,CF₄, NH₄HF₂, HF, SiF₄, KrF₄, XeF₂, XeF₄, and NF₃, and thefluorine-containing substance may be at least one selected from thegroup consisting thereof and may be preferably at least one selectedfrom the group consisting of F₂ and HF.

When the fluorine-containing substance is in the solid state or theliquid state at ordinary temperature, the first fluoride phosphor andthe fluorine-containing substance may be mixed and brought into contactwith each other. The first fluoride phosphor may be mixed with thefluorine-containing substance accounting for, for example, 1 mass % ormore and 20 mass % or less, preferably 2 mass % or more and 10 mass %,in terms of mass of fluorine atoms, based on 100 mass % of the totalamount of the first fluoride phosphor and the fluorine-containingsubstance.

The temperature at the time of mixing the first fluoride phosphor andthe fluorine-containing substance may be, for example, a temperaturelower than the heat treatment temperature from room temperature (20°C.±5° C.) or may be the heat treatment temperature. Specifically, thetemperature may be 20° C. or higher and lower than 400° C., or 400° C.or higher. When the temperature at the time of bringing the firstfluoride phosphor into contact with the fluorine-containing substance ina solid state or liquid state at ordinary temperature is 20° C. orhigher and lower than 400° C., the heat treatment is performed at atemperature of 400° C. or higher after the first fluoride phosphor andthe fluorine-containing substance are brought into contact with eachother.

When the fluorine-containing substance is a gas, the first fluoridephosphor may be placed in an atmosphere containing thefluorine-containing substance and brought into contact therewith. Theatmosphere containing the fluorine-containing substance may contain aninert gas such as a rare gas or nitrogen in addition to thefluorine-containing substance. In this case, the concentration of thefluorine-containing substance in the atmosphere may be, for example, 3vol. % or more and 35 vol. % or less, preferably 5 vol. % or more or 10vol. % or more, and preferably 30 vol. % or less or 25 vol. % or less.

The heat treatment may be performed by retaining the heat treatmenttemperature for a predetermined time while the first fluoride phosphorand the fluorine-containing substance are in contact with each other.The heat treatment temperature may be, for example, 400° C. or higher,preferably a temperature higher than 400° C., 425° C. or higher, 450° C.or higher, or 480° C. or higher. The upper limit of the heat treatmenttemperature may be, for example, less than 600° C., preferably 580° C.or lower, 550° C. or lower, or 520° C. or lower.

When the heat treatment temperature is equal to or higher than the lowerlimit, fluorine atoms are sufficiently supplied to the first fluoridephosphor, and the luminance of the second fluoride phosphor obtained bythe heat treatment tends to be further improved. When the heat treatmenttemperature is not more than the upper limit value, the decomposition ofthe second fluoride phosphor obtained by the heat treatment is moreeffectively suppressed, and the luminance of the obtained secondfluoride phosphor tends to be further improved.

The heat treatment time in the heat treatment step, i.e., the time forretaining the heat treatment temperature may be, for example, 1 hour ormore and 40 hours or less, preferably 2 hours or more or 3 hours ormore, and preferably 30 hours or less, 10 hours or less, or 8 hours orless. When the heat treatment time at the heat treatment temperature iswithin the range, fluorine atoms may sufficiently be supplied to thefirst fluoride phosphor. As a result, the crystal structure of thesecond fluoride phosphor becomes more stable, and a second fluoridephosphor having high luminance tends to be obtained.

The pressure in the heat treatment step may be atmospheric pressure,0.101 MPa, more than atmospheric pressure and 5 MPa or less, or morethan atmospheric pressure and 1 MPa or less.

The method for producing a fluoride phosphor may include a granulatingstep in which treatments such as crushing, pulverization, andclassification operations are combined and performed for theheat-treated product obtained after the heat treatment step. A powderhaving a desired particle size may be obtained by the granulating step.Fluoride Phosphor

The fluoride phosphor obtained by the method for producing a fluoridephosphor described above may be the first fluoride phosphor or thesecond fluoride phosphor. The fluoride phosphor has a compositioncontaining the alkali metal, the element M¹, the element M², manganese(Mn), and fluorine (F). In the composition of the fluoride phosphor,when the total number of moles of the alkali metal is assumed as 2, thetotal number of moles of the element M¹, the element M², and Mn may be0.9 or more and 1.1 or less, preferably 0.95 or more and 1.05 or less,or 0.97 or more and 1.03 or less. The ratio of the number of moles ofthe element M¹ to the total number of moles of the alkali metal of 2 maybe, for example, more than 0 and 0.2 or less, preferably more than 0 and0.1 or less, 0.002 or more and 0.07 or less, or 0.003 or more and 0.05or less. The ratio of the number of moles of Mn to the total number ofmoles of the alkali metal of 2 may be, for example, more than 0 and 0.2or less, preferably 0.005 or more and 0.15 or less, and 0.01 or more and0.12 or less, or 0.015 or more and 0.1 or less. The ratio of the numberof moles of F to the total number of moles of the alkali metal of 2 maybe, for example, 5.9 or more and 6.1 or less, preferably 5.92 or moreand 6.05 or less, or 5.95 or more and 6.025 or less. In the compositionof the fluoride phosphor, the ratio of the number of moles of theelement M² to the total number of moles of the alkali metal of 2 may be,for example, 0.7 or more and 1.1 or less, preferably 0.8 or more and1.03 or less, 0.85 or more and 1.01 or less, or 0.90 or more and lessthan 0.96. In the composition of the fluoride phosphor, the ratio of thenumber of moles of the element M¹ to the number of moles of the elementM² may be, for example, 0.001 or more and 0.1 or less, preferably 0.002or more and 0.07 or less, or 0.003 or more and 0.05 or less.

The fluoride phosphor may have a composition represented by Formula (I).

M³ ₂[M² _(p)M¹ _(q)Mn_(r)F_(s)]  (I)

In Formula (I), M¹ contains at least one selected from the groupconsisting of group 13 elements. M² contains at least one selected fromthe group consisting of group 4 elements and group 14 elements. M³contains at least one selected from the group consisting of alkalimetals. Mn may be a tetravalent Mn ion. In Formula (I), p, q, r, and smay satisfy 0.95≤p+q+r≤1.1, 0≤q≤0.2, 0≤r≤0.2, 5.9≤s≤6.1. Preferably,0.95≤q+q+r≤1.05 or 0.97≤+q+r≤1.03, 0<q≤0.1, 0.002≤q≤0.07 or0.003≤q≤0.05, 0.005≤r≤0.15, 0.01≤r≤0.12 or 0.015≤r≤0.1, 5.92≤s≤6.05 or5.95≤s≤6.025.

M¹ may be at least one selected from the group consisting of group 13elements. Examples of the group 13 element include B, Al, Ga, and In. M¹may preferably contain at least Al. The ratio of the number of moles ofAl to the total number of moles of M¹ in the composition of the fluoridephosphor may be, for example, 0.85 or more, preferably 0.9 or more, or0.95 or more.

M² may be at least one selected from the group consisting of group 4elements and group 14 elements. Examples of the group 4 element includeTi, Zr, and Hf. Examples of the group 14 element include C, Si, Ge, Sn,and Pb. M² may be at least one selected from the group consisting of atleast Ti, Zr, Hf, Si, Ge, and Sn, preferably Si or Si and Ge, and may beSi. The ratio of the number of moles of Si to the total number of molesof M² in the composition of the fluoride phosphor may be, for example,0.8 or more, preferably 0.85 or more, or 0.9 or more.

M³ may be at least one selected from the group consisting of alkalimetals. Examples of the alkali metal include Li, Na, K, Rb, and Cs, andat least one selected from the group consisting of these may be used. M³may contain at least K. The ratio of the number of moles of K to thetotal number of moles of M³ in the composition of the fluoride phosphormay be, for example, 0.7 or more, preferably 0.8 or more, or 0.85 ormore.

In M³, a portion of the alkali metal may be replaced with ammonium ions(NH₄ ⁺). When a portion of the alkali metal is replaced with ammoniumions, the ratio of the number of moles of ammonium ions to the totalnumber of moles of alkali metal contained in the composition of thefluoride phosphor may be, for example, 0.10 or less, preferably 0.05 orless, or 0.03 or less. The lower limit of the ratio of the number ofmoles of ammonium ions may be, for example, more than 0, preferably0.005 or more.

The average particle diameter of the fluoride phosphor may be, forexample, 5 μm or more and 90 μm or less, preferably 10 μm or more, or 15μm or more, and preferably 70 μm or less or 50 μm or less, from theviewpoint of improving the emission intensity of the light emittingdevice.

The volume-based center particle diameter of the fluoride phosphor maybe, for example, 5 μm or more and 90 μm or less, preferably 10 μm ormore, 15 μm or more, or 20 μm or more, and preferably 70 μm or less, 60μm or less, or 50 μm or less, from the viewpoint of improving theemission intensity of the light emitting device. The particle sizedistribution of the fluoride phosphor may exhibit a single peak particlesize distribution from the viewpoint of improving the emission intensityof the light emitting device, for example.

The fluoride phosphor is, for example, a phosphor activated withtetravalent manganese, absorbs light in a short wavelength region ofvisible light, and emits red light. The excitation light may mainly belight in the blue region, and the peak wavelength of the excitationlight may be, for example, in the wavelength range of 380 nm or more and485 nm or less. The luminescence peak wavelength in the emissionspectrum of the fluoride phosphor may be, for example, in the wavelengthrange of 610 nm or more and 650 nm or less. The half-value width in theemission spectrum of the fluoride phosphor may be, for example, 10 nm orless.

The fluoride phosphor may include a cubic crystal structure, may includeother crystal structures such as a hexagonal system in addition to thecubic crystal structure, or may substantially be composed only of acubic crystal structure. The term “substantially” as used herein meansthat the content percentage of the crystal structure other than thecubic system is less than 0.5%. When the fluoride phosphor contains acubic crystal structure, the lattice constant thereof may be, forexample, 0.81380 nm or more, preferably 0.81400 nm or more, or 0.81425nm or more. The upper limit of the lattice constant may be, for example,0.81500 nm or less. The fluoride phosphor containing a cubic crystalstructure and the lattice constant thereof may be evaluated by measuringan X-ray diffraction pattern of the fluoride phosphor. The X-raydiffraction pattern is measured by using, for example, CuKα rays(λ=0.15418 nm, a tube voltage of 40 kV, a tube current of 40 mA) as anX-ray source.

In an infrared absorption spectrum, the fluoride phosphor may have anabsorption peak in a wavenumber range of, for example, 590 cm⁻¹ or moreand 610 cm⁻¹ or less, preferably 593 cm⁻¹ or more and 607 cm⁻¹ or less,or 595 cm⁻¹ or more and 605 cm⁻¹ or less. An absorption peak in apredetermined wavenumber range is considered to be derived from, forexample, an Al—F bond in a cubic crystal structure. The infraredabsorption spectrum is measured by an attenuated total reflection (ATR)method, for example.

The fluoride phosphor may have unevenness, grooves, etc. on the particlesurface thereof. The state of the particle surface may be evaluated, forexample, by measuring an angle of repose of powder composed of thefluoride phosphor. The angle of repose of the powder composed of thefluoride phosphor may be, for example, 70° or less, preferably 65° orless, or 60° or less. The lower limit of the angle of repose is, forexample, 30° or more. The angle of repose is measured, for example, bythe infusion method.

Light Emitting Device

The light emitting device includes a first phosphor containing thefluoride phosphor and a light emitting element having a luminescencepeak wavelength in a wavelength range of 380 nm or more and 485 nm orless.

An example of a light emitting device will be described with referenceto a drawing. FIG. 1 is a schematic cross-sectional view showing anexample of the light emitting device according to this embodiment. Thislight emitting device is an example of a surface mount type lightemitting device. A light emitting device 100 includes a light emittingelement 10 and a molded body 40 on which the light emitting element 10is placed. The molded body 40 has a first lead 20 and a second lead 30and is integrally molded from a thermoplastic resin or a thermosettingresin. The molded body 40 is provided with a recess having a bottomsurface and a side surface, and the light emitting element 10 is placedon the bottom surface of the recess. The light emitting element 10 has apair of positive and negative electrodes, and the pair of positive andnegative electrodes is electrically connected to the first lead 20 andthe second lead 30 via wires 60. The light emitting element 10 is sealedby a fluorescent member 50. The fluorescent member 50 contains aphosphor 70 containing a fluoride phosphor converting a wavelength ofthe light from the light emitting element 10. The phosphor 70 mayinclude a first phosphor containing the fluoride phosphor and a secondphosphor emitting light having a luminescence peak wavelength in awavelength range different from that of the fluoride phosphor due tolight from the light emitting element 10.

The fluorescent member may contain a resin and a phosphor. Examples ofthe resin constituting the fluorescent member include silicone resin andepoxy resin. The fluorescent member may further contain a lightdiffusing material in addition to the resin and the phosphor.

The light emitting element emits light having a luminescence peakwavelength in a wavelength range of 380 nm or more and 485 nm or less,which is a short wavelength region of visible light. The light emittingelement may be an excitation light source exciting the fluoridephosphor. The light emitting element preferably has a luminescence peakwavelength in a range of 380 nm or more and 480 nm or less. For example,a semiconductor light emitting element using a nitride-basedsemiconductor may be used as the light emitting element. The half-valuewidth of the emission peak in the emission spectrum of the lightemitting element is preferably 30 nm or less, for example.

The fluoride phosphor is contained, for example, in a fluorescent membercovering the light emitting element. In the light emitting device withthe light emitting element covered with the fluorescent membercontaining the fluoride phosphor, a portion of the light emitted fromthe light emitting element is absorbed by the fluoride phosphor andemitted as red light.

The second phosphor may be contained in the fluorescent member in thesame manner as the first phosphor, for example. The second phosphor mayhave a composition represented by Formula (IIa), (IIb), (IIc), (lId),(IIe), (IIf), (IIg), or (IIh).

si₆₋₁Al_(t)O_(t)N_(8-t):Eu  (IIa)

(where t is a number satisfying 0≤4.2)

(Ca,Sr,Ba)₈MgSi₄O₁₆(F,Cl,Br)₂:Eu  (IIb)

(Ba,Sr,Ca,Mg)₂SiO₄:Eu(IIc)

(Y,Lu,Gd,Tb)₃(Al,Ga)₅O₁₂:Ce  (IId)

CsPb(F,Cl,Br,1)₃  (He)

(La,Y,Gd)₃Si₆N₁₁:Ce  (IIf)

(Sr,Ca)LiAl₃N₄:Eu  (IIg)

(Ca,Sr)AlSIN₃:Eu  (IIh)

In the formulae, multiple elements separated by commas (,) in theformula representing the composition of the phosphor means that at leastone element among multiple elements is contained in the composition. Inthe formula representing the composition of the phosphor, a mothercrystal is represented before a colon (:), and an activating element isrepresented after a colon (:).

EXAMPLES

The present invention will hereinafter specifically be described withreference to Examples; however, the present invention is not limited tothese Examples.

Example 1 Providing Step

A first solution was prepared by weighing and dissolving 3.93 g ofK₂MnF₆ and 3.90 g of Al(OH)₃ in a mixed solution of 220 g ofhydrofluoric acid (55 w %) and 20 g of pure water. A second solution wasprepared by mixing 97.3 g of an H₂SiF₆ aqueous solution (40 wt %) and 20g of pure water. Subsequently, 63.10 g of KHF₂ was weighed and dissolvedin a mixed solution of 57.8 g of hydrofluoric acid (55 wt %) and 20 g ofpure water to prepare a third solution.

Synthesis Step

While the first solution was stirred at room temperature (25° C.), thesecond solution and the third solution were added dropwise independentlyof each other and substantially simultaneously over about 5 minutes. Anobtained precipitate was separated into solid and liquid, washed withethanol, and dried at 100° C. for 10 hours. Subsequently, in anatmosphere having a fluorine gas (F₂) concentration of 20 vol. % and anitrogen gas (N₂) concentration of 80 vol. %, the heat treatment isperformed in contact with fluorine gas at a temperature of 500° C. and aheat treatment time of 5 hours to prepare fluoride particles of Example1.

Example 2

A fluoride phosphor of Example 2 was prepared in the same manner as inExample 1 except that K₂MnF₆ and AJ(OH)₃ were dissolved only in 220 g ofhydrofluoric acid without using pure water in the preparation of thefirst solution, that the amount of pure water was changed from 20 g to15 g in the preparation of the second solution, and that the amount ofpure water was changed from 20 g to 15 g in the preparation of the thirdsolution.

Example 3

A fluoride phosphor of Example 3 was prepared in the same manner as inExample 1 except that 4.32 g of K₂MnF₆ and 13.70 g of Al(OH)₃ wereweighed and dissolved in 263 g of hydrofluoric acid (55 wt %) to preparethe first solution, that 95.0 g of the H₂SiF₆ aqueous solution (40 wt %)was used as the second solution, and that KHF₂ was dissolved in 57.8 gof hydrofluoric acid (55 wt %) without using pure water in thepreparation of the third solution.

Comparative Example 1

A solution A was prepared by weighing and dissolving 29.20 g of KHF₂ and11.13 g of K₃AlF₆ in 195 g of hydrofluoric acid (55 wt %). A solution Bwas prepared by weighing and dissolving 4.74 g of K₂MnF₆ in a mixedsolution of 60.8 g of H₂SiF₆ aqueous solution (40 wt %), 225 g ofhydrofluoric acid (55 wt %), and 45 g of pure water.

While the solution B was stirred at room temperature, the solution A wasadded dropwise over about 2 minutes while stirring at room temperature.An obtained precipitate was separated into solid and liquid, washed withethanol, and dried at 100° C. for 10 hours to prepare fluoride particlesof Comparative Example 1.

Comparative Example 2

A fluoride phosphor of Comparative Example 2 was prepared in the samemanner as in Comparative Example 1 except that 21.42 g of KHF₂ and 20.34g of K₃AlF₆ were weighed and dissolved in 205 g of hydrofluoric acid (55wt %) to prepare the solution A and that 4.74 g of K₂MnF₆ was weighedand dissolved in a mixed solution of 60.8 g of H₂SiF₆ aqueous solution(40 wt %), 190 g of hydrofluoric acid (55 wt %), and 30 g of pure waterto prepare the solution B.

Comparative Example 3

A fluoride phosphor of Comparative Example 3 was prepared in the samemanner as in Comparative Example 1 except that 5.86 g of KHF₂ and 38.74g of K₃AlF₆ were weighed and dissolved in 225 g of hydrofluoric acid (55wt %) to prepare the solution A and that 4.74 g of K MnF₆ was weighedand dissolved in a mixed solution of 60.8 g of H₂SiF₆ aqueous solution(40 wt %) and 110 g of hydrofluoric acid (55 wt %) to prepare thesolution B.

Average Particle Diameter

The average particle diameter of the fluoride phosphor obtained asdescribed above was measured by using Fisher Sub-Sieve Sizer Model 95(manufactured by Fisher Scientific). The results are shown in Table 1.

Central Particle Diameter

The central particle size of the fluoride phosphor obtained as describedabove was measured by using a laser diffraction particle diameterdistribution device (MASTER SIZER 2000 manufactured by MALVERN). Theresults are shown in Table 1.

Composition

Each of the obtained fluoride phosphors of Examples and ComparativeExamples was subjected to composition analysis by inductively coupledplasma-atomic emission spectroscopy (ICP-AES) to calculate a molarcontent ratio of each element when the potassium contained in thecomposition was 2 mol. The molar content ratio of fluorine wascalculated by subtracting the molar content ratio of aluminum from thetotal molar content ratio of fluorine and aluminum assuming as 6 mol.The results are shown in Table 1.

Production of Light Emitting Device

Each fluoride phosphor obtained as described above was used as the firstphosphor. A β-sialon phosphor having a composition represented bySi_(5.81)Al_(0.19)O_(0.19)N_(7.81):Eu and a luminescence peak wavelengthnear 540 nm was used as the second phosphor. A resin composition wasobtained by mixing the phosphor 70 containing the first phosphor and thesecond phosphor so that x is 0.280 and y is around 0.270 in chromaticitycoordinates in the CIE1931 color system, with a silicone resin. Themolded body 40 having a recess as shown in FIG. 1 was prepared, andafter the light emitting element 10 made of a gallium nitride-basedcompound semiconductor having a luminescence peak wavelength of 451 nmwas placed on the first lead 20 on the bottom surface of the recess, theelectrodes of the light emitting element 10 were respectively connectedto the first lead 20 and the second lead 30 by the wires 60. The resincomposition was further injected into the recess of the molded body 40by using a syringe so as to cover the light emitting element 10, and theresin composition was cured to form a fluorescent member to produce thelight emitting device.

Relative Luminous Flux

The luminous flux of the light emitting device using each of thefluoride phosphors was measured by using a total luminous flux measuringdevice using an integrating sphere. Assuming that the luminous flux ofthe light emitting device using the fluoride phosphor according toComparative Example 1 was 100%, the luminous flux of the light emittingdevice using the other fluoride phosphors was obtained as a relativeluminous flux (initial luminous flux). The results are shown in Table 1.

Durability Evaluation

The light emitting device obtained as described above was continuouslylit at a current of 150 mA in a high temperature environmental testmachine at 85° C., and a difference from an initial value of the x valuein the chromaticity coordinates after 500 hours was defined as Δx toevaluate the durability of the light emitting device. The results areshown in Table 1.

TABLE 1 Average Central Relative Particle Particle Luminous DiameterDiameter Composition (molar ratio) Flux Durability (μm) (μm) K Si F MnAl (lm) Δx Example 1 26.5 34.9 2.000 0.946 5.996 0.050 0.004 103.4 0.003Example 2 24.5 33.9 2.000 0.940 5.991 0.051 0.009 104.0 0.004 Example 327.0 47.5 2.000 0.919 5.968 0.049 0.032 102.4 0.005 Comparative 27.042.1 2.000 0.947 5.996 0.049 0.004 100.0 0.006 Example 1 Comparative25.0 40.6 2.000 0.942 5.991 0.049 0.009 99.7 0.006 Example 2 Comparative22.5 39.5 2.000 0.932 5.981 0.049 0.019 98.0 0.008 Example 3

As shown in Table 1, the light emitting devices manufactured by usingthe fluoride phosphors obtained by the producing method of Examples hadhigher initial luminous flux and more excellent durability thanComparative Examples.

The fluoride phosphor obtained by the producing method of the presentdisclosure is particularly used in a light emitting device using a lightemitting diode as an excitation light source and may suitably be usedfor, for example, a light source for lighting, a light source for an LEDdisplay or a liquid crystal backlight, a traffic light, illuminationtype switches, various sensors, various indicators, and small strobes.

It is to be understood that although the present invention has beendescribed with regard to preferred embodiments thereof, various otherembodiments and variants may occur to those skilled in the art, whichare within the scope and spirit of the invention, and such otherembodiments and variants are intended to be covered by the followingclaims.

Although the present disclosure has been described with reference toseveral exemplary embodiments, it is to be understood that the wordsthat have been used are words of description and illustration, ratherthan words of limitation. Changes may be made within the purview of theappended claims, as presently stated and as amended, without departingfrom the scope and spirit of the disclosure in its aspects. Although thedisclosure has been described with reference to particular examples,means, and embodiments, the disclosure may be not intended to be limitedto the particulars disclosed; rather the disclosure extends to allfunctionally equivalent structures, methods, and uses such as are withinthe scope of the appended claims.

One or more examples or embodiments of the disclosure may be referred toherein, individually and/or collectively, by the term “disclosure”merely for convenience and without intending to voluntarily limit thescope of this application to any particular disclosure or inventiveconcept. Moreover, although specific examples and embodiments have beenillustrated and described herein, it should be appreciated that anysubsequent arrangement designed to achieve the same or similar purposemay be substituted for the specific examples or embodiments shown. Thisdisclosure may be intended to cover any and all subsequent adaptationsor variations of various examples and embodiments. Combinations of theabove examples and embodiments, and other examples and embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the description.

In addition, in the foregoing Detailed Description, various features maybe grouped together or described in a single embodiment for the purposeof streamlining the disclosure. This disclosure may be not to beinterpreted as reflecting an intention that the claimed embodimentsrequire more features than are expressly recited in each claim. Rather,as the following claims reflect, inventive subject matter may bedirected to less than all of the features of any of the disclosedembodiments. Thus, the following claims are incorporated into theDetailed Description, with each claim standing on its own as definingseparately claimed subject matter.

The above disclosed subject matter shall be considered illustrative, andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments which fall within thetrue spirit and scope of the present disclosure. Thus, to the maximumextent allowed by law, the scope of the present disclosure may bedetermined by the broadest permissible interpretation of the followingclaims and their equivalents, and shall not be restricted or limited bythe foregoing detailed description.

All publications, patent applications, and technical standards mentionedin this specification are herein incorporated by reference to the sameextent as if each individual publication, patent application, ortechnical standard was specifically and individually indicated to beincorporated by reference.

What is claimed is:
 1. A method for producing a fluoride phosphor,comprising: providing a first solution containing an element M¹containing at least one selected from the group consisting of group 13elements, manganese, and fluorine, a second solution containing anelement M² containing at least one selected from the group consisting ofgroup 4 elements and group 14 elements, and a third solution containingat least one selected from the group consisting of alkali metalelements; and adding the second solution and the third solution to thefirst solution at substantially the same time to obtain a first fluoridephosphor.
 2. The method for producing a fluoride phosphor according toclaim 1, wherein the element M¹ contains at least aluminum.
 3. Themethod for producing a fluoride phosphor according to claim 1, whereinthe element M² contains at least silicon.
 4. The method for producing afluoride phosphor according to claim 1, wherein the first solutioncontains an aluminum compound, hexafluoromanganate and hydrofluoricacid.
 5. The method for producing a fluoride phosphor according to claim1, wherein the second solution is substantially composed ofhexafluorosilicic acid and water.
 6. The method for producing a fluoridephosphor according to claim 1, further comprising heat-treating thefirst fluoride phosphor in contact with a fluorine-containing substanceat a heat treatment temperature of 400° C. or higher to obtain a secondfluoride phosphor.
 7. The method for producing a fluoride phosphoraccording to claim 6, wherein the fluorine-containing substancecomprises at least one selected from the group consisting of NH₄F, F₂,CHF₃, CF₄, NH₄HF₂, HF, SiF₄, KrF₄, XeF₂, XeF₄, and NF₃.
 8. The methodfor producing a fluoride phosphor according to claim 6, wherein when thefluorine-containing substance is in a solid state or a liquid state atordinary temperature, an amount of the fluorine-containing substance is1 mass % or more and 20 mass % or less, in terms of mass of fluorineatoms, based on 100 mass % of a total amount of the first fluoridephosphor and the fluorine-containing substance.
 9. The method forproducing a fluoride phosphor according to claim 6, wherein when thefluorine-containing substance is a gas, an amount of thefluorine-containing substance in a heat-treating atmosphere is 3 vol. %or more and 35 vol. % or less.
 10. The method for producing a fluoridephosphor according to claim 6, wherein the heat treatment temperature is425° C. or higher and less than 600° C.
 11. The method for producing afluoride phosphor according to claim 6, wherein a heat treatment time is1 hour or more and 40 hours or less.
 12. The method for producing afluoride phosphor according to claim 6, wherein a pressure in theheat-treating is atmospheric pressure or more and 5 MPa or less.
 13. Themethod for producing a fluoride phosphor according to claim 6, furthercomprising a granulating procedure that includes crushing,pulverization, and classification operation.
 14. The method forproducing a fluoride phosphor according to claim 1, wherein the firstfluoride phosphor contains an element containing at least one selectedfrom the group consisting of alkali metals, an element M¹ containing atleast one selected from the group consisting of group 13 elements, anelement M² containing at least one selected from the group consisting ofgroup 4 elements and group 14 elements, manganese, and fluorine, whereinthe fluoride phosphor has a composition in which, when a total number ofmoles of the alkali metal is 2, a total number of moles of the elementM¹, the element M², and the manganese is 0.9 or more and 1.1 or less, anumber of moles of the element M¹ is more than 0 and 0.2 or less, anumber of moles of the manganese is more than 0 and 0.2 or less, and anumber of moles of the fluorine is 5.9 or more and 6.1 or less.
 15. Themethod for producing a fluoride phosphor according to claim 1, whereinthe first fluoride phosphor has a composition represented by thefollowing Formula:M³ ₂[M² _(p)M¹ _(q)Mn_(r)F_(s)] wherein M¹ contains at least oneselected from the group consisting of group 13 elements, M² contains atleast one selected from the group consisting of group 4 elements andgroup 14 elements, M³ contains at least one selected from the groupconsisting of alkali metals, 0.9≤p+q+r≤1.10<q≤0.2,0<r≤0.2, and5.9≤s≤6.1.
 16. The method for producing a fluoride phosphor according toclaim 1, wherein the second solution consists essentially ofhexafluorosilicic acid and water.